Compression unions are used in low-pressure applications such as: air, oil, and water. They are generally used to connect lengths of copper, brass, and aluminum tubing. To make connection, place the nut and then the sleeve over the tubing and then insert tube into the fitting body. When tight, the wedging action of sleeve between body and nut create a leak free connection. AGS brass and steel fittings are comprised of Tube Nuts, Unions (Couplers), Adapters, Elbows, Tees, Bushings, Connectors, Grease, etc… AGS fittings are held to the strictest standards to perform flawlessly in their intended applications. Fittings are offered in a variety of packaging options, including: retail clam-shells, bulk boxed, and plastic tray assortments.